Ultrathin Hydrophobic Photothermal Distillation Membrane for Enhancing Water Flux in Seawater Desalination

Photothermal membrane distillation (PMD) is a promising strategy for seawater desalination that enables efficient vapor generation by localized heating on the membrane-water interface via photothermal effects. However, conventional PMD membranes suffer from excessive thickness and weak hydrophobicity of pore surfaces that induce undesirable transport resistance and pore wetting. Here, we develop an ultrathin PMD membrane with an ultrathin hydrophobic photothermal layer for enhancing the water flux and stability in seawater desalination. The ultrathin photothermal layer fabricated through a droplet superspreading strategy locally heats seawater, accelerating interfacial evaporation and shortening the vapor transport pathway. Integrated on a porous nanocomposite substrate with robust antiwettability, the optimized PMD membrane (thickness ∼ 20 μm) achieves a 97.8% water flux increase (achieving 18.76 ± 0.1 kg·m–2·h–1) under 1-sun illumination and a salt rejection rate exceeding 99.8% over 30 h. This work provides a promising way to design high-performance PMD membranes, enabling sustainable seawater desalination.